linux-kernel - Re: [PATCH 2/2] net: mdio: support c45 peripherals on c22 busses

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Message-ID: <YGwL67WBGKbWU3TH@arch-linux>
Date:   Tue, 6 Apr 2021 09:21:15 +0200
From:   Danilo Krummrich <danilokrummrich@...develop.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        davem@...emloft.net, hkallweit1@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, jeremy.linton@....com
Subject: Re: [PATCH 2/2] net: mdio: support c45 peripherals on c22 busses

On Tue, Apr 06, 2021 at 12:30:11AM +0200, Danilo Krummrich wrote:
> On Mon, Apr 05, 2021 at 09:27:44PM +0200, Andrew Lunn wrote:
> > > Now, instead of encoding this information of the bus' capabilities at both
> > > places, I'd propose just checking the mii_bus->capabilities field in the
> > > mdiobus_c45_*() functions. IMHO this would be a little cleaner, than having two
> > > places where this information is stored. What do you think about that?
> > 
> > You will need to review all the MDIO bus drivers to make sure they
> > correctly set the capabilities. There is something like 55 using
> > of_mdiobus_register() and 45 using mdiobus_register(). So you have 100
> > drivers to review.
> Yes, but I think it would be enough to look at the drivers handling the
> MII_ADDR_C45 flag, because those are either
> - actually capable to do C45 bus transfers or
> - do properly return -EOPNOTSUPP.
> 
> I counted 27 drivers handling the MII_ADDR_C45 flag. Setting the capabilities
> for those should be pretty easy.
> 
> The remaining ones, which should be about 73 then, could be left untouched,
> because the default capability MDIOBUS_NO_CAP would indicate they can C22 only.
> Since they don't handle the MII_ADDR_C45 flag at all, this should be the
> correct assumption.
Forgot to mention, this would also automatically fixup that userspace C45
requests for those "remaining" drivers results in garbage on the bus. :-)
> > 
> > 	Andrew
> >